Biosensor test member and method for making the same

ABSTRACT

A biological test member, and method of making the same, is disclosed with the member including a substrate. The test member has usefulness, for example, in testing a person&#39;s blood glucose level. A first layer and a second layer of conductive metal are printed or otherwise applied on the substrate in an electrode pattern. The metal or metals are cured or sintered at a low, non-damaging temperature, such as by applying one or more pulses of a high-energy broad spectrum light. A layer of reagent may be provided on said second metal layer.

This application is a divisional of application Ser. No. 12/862,262,filed Aug. 24, 2010, which is hereby incorporated by reference, andpriority is claimed thereon.

FIELD OF INVENTION

The present invention is in the field of biosensor testing members, suchas for example, test strips. These have usefulness, for example, intesting a person's blood glucose level.

BACKGROUND

The present invention is an improvement on prior test strips and howthey are made. The present test members have usefulness in a variety ofindications, including but not limited to blood testing (such as forglucose levels), as well as for bG testing, ketone testing, HbA1cstrips, coag testing, continuous monitoring, and otherwise.

Currently, in some strips metal tracks are produced by sputtering a verythin layer of gold across the entire substrate reel and then using laserablation or laser scribing to pattern the tracks, laser ablation inparticular enabling a higher degree of accuracy. This is a subtractiveprocess which results in loss of precious metal (some of which can laterbe reclaimed) as well as significant energy usage.

Other methods involve additive steps, such as inkjet printing andotherwise, to the extent disclosed in U.S. Patent Publication Nos.2005/0130397 and 2005/0153078 to Bentley et al., but fail to discloseother features and benefits set forth herein.

One object is to provide an improved test member and a method for makingthe same.

SUMMARY

This object and others that may be set forth herein or otherwiseappreciated by those of ordinary skill in the art in view of thisdisclosure are achieved by the present invention. The present inventionmay include a biosensor test member which may include a substrate and aconductive layer of one or more metals, normally in an electrodepattern. These metals may be alone or combined, or in separate layers,abutting, and/or a combination thereof. They may be sintered together.One or more pulses of high-energy, broad spectrum light may be used tosinter the metals. In certain aspects of the present invention, exposureto such pulses for any purpose may be referred to as “pulse forging”.The metals may be applied by printing, high speed or otherwise. They maybe in an ink carrier and cured on the substrate.

Also, a layer of electrically conductive first metal may be provided ona layer of ink substantially coinciding with said electrode pattern.There may also be another layer of electrically conductive metalthereon. Typically, the second metal is different from the first metal.Normally, a layer of reagent is put on that metal layer, and in oneembodiment that second metal is substantially non-reactive to thereagent.

Electrical traces having different electrical resistivity may be on thetest strip, such as for machine readable calibration, lot identificationor otherwise. Such resistivity may be controlled by using differentamounts of curing, such as by one or more pulses of high-energy, broadspectrum light, for different traces or portions thereof.

The present invention may include methods of producing a test member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-1 is a top plan view of one example of a device according to thepresent invention. FIG. 1A-1 shows three such devices grouped or gangedon a single substrate, for later separation.

FIG. 1A-2 is a bottom plan view of one example of a device according tothe present invention. FIG. 1A-2 shows three such devices grouped organged on a single substrate, for later separation.

FIG. 1B is a top plan detail of the device of FIG. 1A.

FIG. 1C is a partial side cross-section through an electrical trace ofthe device of FIG. 1A.

FIG. 1D is an alternative partial side cross-section through anelectrical trace.

FIG. 1E is an alternative partial side cross-section through anelectrical trace.

FIG. 1F is an alternative partial side cross-section through anelectrical trace.

FIG. 2 is a photograph of conductive inkjet technology (“CIT”) ink on asubstrate.

FIG. 3 is a photograph of CIT ink plated with electroless copper on asubstrate.

FIG. 4 is a photograph of CIT ink plated with electroless copper andelectroless gold on a substrate.

FIG. 5. is a photograph of CIT ink plated with electroless copper andimmersion gold on a substrate.

FIG. 6 is photograph of thin-film CIT ink on a substrate.

FIG. 7 is a photograph of thin-film CIT ink plated with electrolesscopper on a substrate.

FIG. 8 is a photograph of thin-film CIT ink plated with electrolesscopper and electroless gold on a substrate.

FIG. 9 is a photograph of thin-film CIT ink plated with electrolesscopper and immersion gold on a substrate.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the examples, sometimesreferred to as embodiments, illustrated and/or described herein. Thoseare mere examples. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended. Such alterations andfurther modifications in the described processes, systems or devices,any further applications of the principles of the invention as describedherein, are contemplated as would normally occur to one skilled in theart to which the invention relates, now and/or in the future in light ofthis document.

As used in the claims and the specification, the following terms havethe following definitions:

The term “cured ink” means ink in a solid or semi-solid form, havingbeen dried, fused and/or solidified (by evaporation or otherwise),heated, exposed to chemical reaction, and/or exposed to high-energypulsed light and/or some form of energy or radiation, such asultraviolet (UV) light or otherwise, and/or any combination thereof.

The term “electroless plating” means depositing, plating or otherwisecovering a receptive surface without the use of applied electricalcurrent. This includes, but is not limited to immersion plating, such asfor example, immersion plating of gold onto copper or onto nickel oronto both. Note that “electroless” herein is synonymous with the term,“electrode-less”.

The term “electroless plating bath deposit” means a solid deposit,plating or other layer of electrically conductive metal from anelectroless plating process.

The term “high-energy broad spectrum light” means light, (visible,invisible, or both) in the electromagnetic spectrum having: (a) anenergy at or greater than about 180 joules, and optionally but morepreferably greater than about 2000 joules; and, (b) having more than onewavelengths of light having a frequency variance of at least about 180nanometers, and optionally but more preferably a frequency variance ofat least 1100 nanometers apart. This may, but does not necessarilyinclude pulse forging.

The term “high speed printing” means printing at a linear rate of amedium upon which that is being printed about 3 meters per minute orfaster.

The term “inkjet printing” means a printing process in which droplets ofink issuing from nozzles are directed onto a surface, such as asubstrate under computer control. This also encompasses jet printing,continuous jet printing or other printing with any kind of drop-dispensetechnology.

The term “laser ablated” means removal of a material, typically at or todefine an edge, by irradiating it with a laser beam, and herein alsoincludes laser scribing.

The term “low temperature photonic energy” means energy transferred byphotons (including light as well as all other forms of electromagneticradiation, including as a force carrier for electromagnetic force orenergy) in an amount that maintains the average temperature of thematter it is acting upon below about 80 degree Celsius, and optionally,but more preferably below about 26 degrees Celcius. This may, but doesnot necessarily include high-energy broad spectrum light and/or pulseforging.

The term “polymer” means a long molecule made up of a chain of smaller,simpler molecules. This may include a product of polymerization. Thismay be natural, synthetic or both. This may include carbohydrates, suchas cellulose, proteins and plastics. Polymer, as used herein, alsoincludes materials which are combination and/or composite of polymersand non-polymers.

The term “precipitated solute” means a solid plating, layer or otherdeposit of a substance which had been previously dissolved or otherwisesuspended in a solution or bath.

The term “printing” means the application of ink or ink-like material ona solid surface. This may include liquid inks, dry particle inks, andcombinations thereof and otherwise. This may include offset printing,laser and otherwise. Printing may incur with pressure or non-pressure,contact or non-contact, and/or may include electro-static and/ornon-electro-static application.

The term “pulse forging” means exposing to one or more pulses of ahigh-energy photonic energy. This may be a strobe pulse or otherwise. A“pulse” as used herein (such as with respect to pulse forging, lowtemperature photonic energy, and/or high-energy broad spectrum light, orotherwise), indicates that the light is normally applied only for shortdurations, typically between about 100 microseconds and 1 millisecond.Normally, such pulsed light or other energy is not applied continuously,but rather for these short pulse durations.

The term “reagent” is a substance for use in a chemical reaction todetect, measure, examine or produce other substances. In the context ofthe present device these are typically crystalline, powder or othersolid form deposited on the device. For biological testing, typicallythey are for testing the concentration of analytes in the fluid(typically blood or other body fluid). Typically, this is forfacilitating electron transfer between electrodes in such a fluid.Commonly they are or include a glucose enzyme. However, they may be orinclude other enzymes and/or non-enzymes and/or other fillers and/orchemicals.

The term “reference metallic electrical trace” means a trace that isused at least in part for having an electric current pass through it andthe magnitude and/or other attributes of such an electrical currentand/or electrical signal thereof are measured for comparison to someother value.

The term “RFID tag” means a radio frequency identification tag. This maybe active, passive or both. This may be a stand alone, pre-manufacturedtag and/or a printed circuit otherwise.

The term “sinter” means to cause to form a coherent mass, typically ofone or more metals, by heating without melting, by pressure, or by othernon-molten process and/or by a combination thereof.

The term “substrate damage temperature” means the temperature abovewhich a substrate melts, burns, warps, or otherwise substantiallydeforms. This will vary from material to material. Such temperature mayalso be a function of time and temperature.

The language used in the claims is to only have its plain and ordinarymeaning, except as may be explicitly defined herein. Such plain andordinary meaning is inclusive of all consistent dictionary definitionsfrom the most recently published general usage Webster's dictionariesand Random House dictionaries, and is inclusive of the meaning generallygiven to such language according to the general knowledge of a person ofordinary skill in the art.

Referring to the drawing figures, these are only examples of theinvention, and the invention is not limited to what is shown in thedrawings. For an example in the figures, and in particular FIG. 1A-1through FIG. 1F, a biosensor test member 20 may comprises a substrate30, and a layer 40 of cured ink in a printed electrode pattern 80 onsaid substrate. Layer 50 of an electrically conductive first metal isshown overlying the ink 40 and substantially coinciding with saidelectrode pattern 80. Layer 60 of an electrically conductive secondmetal is shown overlying layer 50, also substantially coinciding withthe electrode pattern 80. Typically, the second metal (for example goldor gold alloy) is different from the first metal (for example copper orcopper alloy). A layer of reagent 70 may be provided on and covering themetal layer 60 and/or on substrate 30, typically overlying at least inpart electrode pattern 80. Normally, layer 70 covers substantially morethan just pattern 80, at least at the reaction end 91. Optionally,however, layer 70 could be made to substantially coincide with pattern80, or conversely to substantially not coincide with pattern 80, such aslying interstitially between edges 81 and 82 (see FIG. 1B). A variety oftraces may be provided. For example traces 93 and 94 provide for acircuit with edges 81 and 82 lying in a mid-region of such circuit.Other shapes and arrangements may be used as well. For example, the twocentral traces illustrated may be used for confirming proper dosing.

With reference to FIG. 1A-2, an optional back side of test member 20 maybe illustrated. Substrate 20 is as previously described. Also, aspreviously described, this illustrates three members together whichlater in the production process may be cut or otherwise separated. One,two, three or more reference metallic electrical traces may be present.For example, reference metallic electrical traces 96, 97 and 98 areillustrated as mere examples. These may be used for calibration,identification, lot coding, and/or a combination thereof, and/orotherwise. As illustrated, for example, metallic electrical trace 96 isgenerally “U” shaped, with contact pads at one end, and with the generallength of the trace doubling back from one pad to the next. However, anyarrangement may be used, including having such traces transverse to thewidth of the strip, curvilinear, serpentine, or otherwise. Additionally,reference metallic electrical traces need not necessarily be on the backside of a test strip. They may be on the front side, lateral side and/ora combination thereof as desired, depending on size and spaceconstraints on the front and back surfaces of the substrate 30.Additionally, such reference metallic electrical traces may be presentwith dual or multiple functions. For example, the present inventionoptionally could be modified such that traces 93 and/or 94, or othertraces illustrated in FIG. 1A-2, also function as reference metallicelectrical traces, in addition to other functions.

Optionally, the attributes of such reference traces may be varied. Forexample, curing or other pulse forging or other treatment of respectiveelectric traces 96, 97, 98 different from each other may be done toalter the resistivity of such traces. As such, for example, exposing afirst reference metallic electrical trace 96 to more curing than asecond reference metallic electrical trace 97 and/or 98, may result in adifferential electrical resistivity as between the traces sufficient toallow machine reading of test strip attributes based on thatdifferential. This may include lot coding, calibration, or otherwise.Also, optionally instead of or in addition to varying the time and/orintensity of curing, pulse forging, etc., a differential resistanceand/or resistivity may be accomplished by exposing various lengths ofvarious traces to such curing, pulse forging, etc. This likewise mayvary among all three (96, 97 and 98) or more traces for more codingcombinations.

Layer 70 generally comprises a reagent. In one embodiment, metal 60comprises a material that is substantially non-reactive to reagent 70.Conversely, in other embodiments, reagent 70 is reactive (undesirably,such as corrosive or otherwise) with the first metal layer 50, and isthus generally located so that it does not contact first metal layer 50.In various embodiments, reagent 70 is configured for testing theconcentration of an analyte in a liquid, such as a glucose enzyme orotherwise. Reagent 70 may be printed (such as by inkjet printing) orotherwise applied or coated. One approach is to apply the reagent byinkjetting with piezo electric ink jet heads, which optionally allowsprinting different reagent formulations over and/or adjacent oneanother. Hence, dual layers or more of reagents may be applied. It isalso possible to apply reagents (for example Ag/AgCl chemistries) at ornear a reference electrode to enhance test strip accuracy.

Optionally, one or more hydrophilic compounds may be on part or all ofreaction end 91, substrate 30, or otherwise to facilitate fluid contactwith reagent 70 and/or with electrodes, such as for example at or nearedges 81 and 82. Such hydrophilic agent may be separate from and/orincluded as part of reagent 70.

Metal 50 and metal 60 may be kept as separate masses or may be sinteredtogether. If sintered, they may be sintered essentially as a whole, butalso may be sintered only primarily at their interface. Also, thirdand/or other layers, such as third metal layers (not drawn) may beincluded in the device, sintered or not. Sintering may be accomplishedin any number of known sintering techniques.

FIG. 1D shows an alternative test member 120. This is similar to testmember 20 shown in FIG. 1C except that the layer of ink 40 has beenoptionally omitted. Metal 50 and metal 60 are provided. Reagent 70 isillustrated, but optionally may be omitted as well.

FIG. 1E illustrates test member 220, again another alternative. In thisillustration pattern 80 comprises, and indeed may consist of, or consistessentially of, metal 50. As illustrated, member 220 does not have areagent, though optionally it may have a reagent such as reagent 70shown in FIG. 1D. Metal 50 may be a single metal, and/or may be analloy, and/or it may be a blend or other combination of two or moremetals. For example, metal 50 may be a combination of metal particlessuspended in an ink binder or matrix. Such suspended particles may besubsequently sintered together. Optionally, they may be sintered bypulse forging or otherwise.

FIG. 1F shows another optional example of a test member 320. In thisillustration, pattern 80 is shown as a first metal 50 and second metal60. Note that in this example, such metals abut one another such as atabutment interface 165. As before, optionally, a reagent layer, such asreagent layer 70 (not shown in FIG. 1F) may be provided on top of thepattern 80, or not. It also may be provided over one metal, such asmetal 50, but not the other metal, or partially over one or both. Inaddition to the two metals 50 and 60 abutting at interface 165, one ormore additional layers (not shown) may overlay one or both metalportions 50 and 60, including spanning the abutment 165. As before, suchmetal layers may actually comprise particles or other suspended metal inan ink or carrier, and may be sintered together and/or may be sinteredpartially together at an interface. Similarly, with reference back toFIG. 1D, such partial sintering together in an interface may occur, asshown in FIG. 1D, at the interface between metal 50 and metal 60.

The arrangements of FIGS. 1B, 1C, 1D, 1E and/or 1F, as well as otherarrangements and features as described, may be isolated, combined ormixed and matched with each other. Those are merely samples.

In embodiments in which an ink is used, it is desirable but notgenerally required to select an ink whose curing is accomplished withoutdamage to substrate 30, such as may be caused by excessive time and/ortemperature in heat curing the ink. The ink may be cured optionally byapplying a high-energy strobe pulse of photonic energy to the substrate,before or after the addition of the metal layers 50 and/or 60. Oneexample of an optional treatment includes curing by the PulseForge™ 3100while maintaining the substrate temperature below 50° C. or to otherwisecryogenically treat the metal, normally after it has been formed intolayers 50 and/or 60 on a substrate, and ideally for only short periodsof time.

Conductive metal tracks, also referred to herein as electrode patterns80 (see FIG. 1A-1, 1C) may be produced using inkjet technology viaconductive inkjet technology (CIT) in which a catalytic ink 40 (see e.g.FIG. 1C (not to scale)) is typically printed, cured using UV radiation,and plated with a metal 50 (typically copper or nickel) and/or 60(typically gold). In one embodiment, electroless plating processes areused. Through this method, conductivity approaching that of bulk metalcan be achieved. Optionally, ink 40 may be printed using othertechniques, including laser printing, contact printing, rotary screenprinting, flexo printing, gravure or otherwise. For embodiments in whichinkjet printing is used, high resolution deposition can be advantageousfor optimal use of the resulting biosensor test member. In oneembodiment, an inkjet printer is able to print down to 100 μm lines andspaces and smaller, such as inkjet printing at 600 to 1200 dpi orbetter. However, other resolutions, higher or lower as desired, may beused.

Moreover, as mentioned the conductive metal may reside in, rather thanmerely on, the ink or printing.

In other embodiments, an additive process may be used to apply anelectro-conductive material (e.g. traces 80), such as a metal and/ormetal containing matrix or carrier, to a biosensor test member and then,for example, pulse forge the material to sinter it together. Theadditive process then may result in reducing the amount of materialrequired as compared to a subtraction process such as etching, laserablation or otherwise. The additive approach, alone or in combinationwith subtractive processes, allow similar edge qualities as an ablationtechnique but with less waste of expensive raw materials, such as gold.This also allows the forming of other components on the test strip suchas machine readable and/or non-evident coding components, such as abarcode or a “data matrix code” or “DMC”. In one particular example, thepulse forging allows for different degrees of curing which in turn canallow for the creation of conductive strips (for example, traces 96, 97and/or 98) having different resistivity and/or different resistances andtherefore can be used as identifiers for machine readable and/ornon-evident coding purposes. The additive nature also optionally allowsa zebra-striping to occur in which (multiple) ends of copper are abuttedagainst (multiple) ends of gold or silver (see e.g. FIG. 1F) forming astriping in series. Optionally, other additive techniques besides CITcan be used, such as directly inkjetting the gold or other conductivemetal ink onto the substrate. In one embodiment, a dry manner ofapplication of the ink is used, although other non-dry and/or hybridapproaches may be used. In one instance, a 5 nanometer thickness of goldhas been deposited onto a substrate by inkjetting, although greater orlesser thicknesses may be used. A characteristic of pulse forging isthat it can cure without heating an underlying substrate. This additiveprocess also allows the forming of different metallization areas. Pulseforging further allows machine readable and/or non-evident codingoptionally to be formed without harming any enzymes or other chemistryin a reagent. Pulse forging techniques, furthermore, may allow linespeeds of 30 to 60 meters/minute, and inkjetting allows more heads andallows faster drying which in turn reduces the size of the manufacturingline. Other examples of using this technique allows for the formation ofRFID tags on a strip.

In one embodiment, edges, such as at least edges like 81 and 82 (seee.g. FIGS. 1B and 5), are spaced from each other by a predeterminedspacing and have suitable line acuity for biological testing (such as,for example human blood glucose level testing). Such acuity may bedesired to allow for a reliable, measurable, and predictable currentsignal for testing, e.g., blood glucose levels. In one embodiment, suchedge acuity is less than about 50 μm. In other embodiments, edge acuityis less than about 20 μm, and can be down to less than about 10 μm. Insome of the tested examples, edge acuity ranged on average from about4-6 μm. Also, the standard deviation of the edge acuity ratios istypically less than about 30 μm, and has been shown to be less thanabout 15 μm and as low as less than about 10 μm. Such testing examplesare discussed further, below, regarding line acuity of the edges. Suchedge acuity may be achieved with the present disclosure, notably withoutlaser or other ablation. Nevertheless, laser ablation can provide betterline or edge acuity (e.g. less than an average of one μm), and thepresent invention optionally may be used with laser ablation, or inpartial combination with laser ablation. For example, one may use laserablation to define the edges of the pattern of metal layer 50 (such ascopper), while instead using electroless plating rather than laserablation, to establish the edges or some or all of metal layer 60 (suchas gold). Moreover, one could do this, or complete ablation of layers40, 50 and 60, but only at selected or critical locations, such as forexample, at edges at reaction end 91, such as edges 81 and 82. Theseoptions allow one to reduce waste and cost recovery (such as of gold)while enhancing line or edge acuity and while potentially reducingelectrical resistance from end 91 to end 92.

Metal layer 60 may be reduced in thickness from prior art approaches ofabout 50 nanometers (nm) of gold, to optionally about 15 nm or less,particularly with electroless plating of layer 60. In one embodiment,this new method and device may provide a total metal thickness for atrace (layers 50 and 60 together) of about 50 to 300 nm, with about twopercent (2%) thickness control along the trace.

Some non-limiting examples and testing of CIT ink and thin-film CIT inkare set forth below.

A. EXAMPLES 1-6 Example 1-3

Standard CIT ink was printed onto polyester substrate 30 using anOmnidot 760 GS8 printhead to produce catalytic templates of circuits forbiosensor test members. The original image used as the basis for theprinted circuits is shown in FIG. 1A to form conductive metal circuits,or electrode pattern, used in the present biological test member, e.g. abiosensor. These templates were tack-cured during the printing processusing a low-power UV source (Omnicure S2000. Exfo) in order to controldot gain and then fully cured using a Fusion Lighthammer 6 UV-curringtunnel. This formed Example 1 as shown in FIG. 2.

Thereafter, a first metal layer 50, namely in this case a layer ofcopper, was added, as shown in FIG. 3. This was done with the templatebeing immersed into an Enplate 872 copper plating bath for 2 min at 45°C. to deposit copper. This completed Example 1 and the by-product isshown in FIG. 3.

Examples 2 and 3, shown in FIGS. 4 and 5 respectively, had gold added tothe device of Example 1, per above.

Example 2—Electroless gold on electroless copper: As stated, thetemplates were first immersed into an Enplate 872 copper plating bathfor 2 min at 45° C. to deposit copper, after which they were immersedinto a borohydride-based electroless gold plating bath for 1-4 minutes.Gold was successfully plated over the copper tracks. See FIG. 4.

Example 3—Immersion gold on electroless copper: As stated, the templateswere first immersed into an Enplate 872 copper plating bath for 2minutes at 45° C. Gold was successfully plated over the copper tracks.See FIG. 5.

Example 4-6

Those Examples 1-3 (depicted in FIGS. 2-5) using CIT ink were thenreproduced as Examples 4-6, but for the starting point, Example 4, usingthin-film CIT ink substituted for the CIT ink of Example 1. Thus,Examples 5 and 6 otherwise are like and correspond to Examples 2 and 3,respectively, above. Some of such thin-film ink examples are shown inFIGS. 6-7 (Example 4), FIG. 8 (Example 5) and FIG. 9 (Example 6).

This thin-film ink (see FIG. 6) was solvent-based with a resin bindermatrix to provide adhesion to the substrate. As such, the solids loadingis much lower than that of the Standard CIT ink, which allows muchthinner films to be produced. As with the Standard CIT ink investigation(Examples 1-3), plating tests were performed: electroless gold onelectroless copper (Example 5), and immersion gold on electroless copper(Example 6). This particular thin-film ink has a high solvent contentand therefore wets out on the substrate surface very well. The flow ofthe ink was somewhat reduced by heating the substrate from the reverseside immediately after printing. However, a significant amount ofspreading still occurs.

B. ADHESION TESTING

Testing of adhesion of the tracks formed in Examples 2-3 above (usingstandard CIT ink) to a polyester substrate was performed using the tapetest and showed good adhesion with very little (<10%) of the tracksbeing removed from the substrate. The tracks are also flexible andsufficiently durable to withstand a fingernail scratch test.

In the same testing, tracks formed in Examples 5-6 above (usingthin-film CIT ink) were flexible and durable enough to withstand afingernail scratch test; however, the adhesion was not as strong as thatof the tracks produced using the standard CIT ink with about 50% of themetal lifting off during the tape adhesion test.

C. LINE QUALITY Line Width and Edge Acuity

Ink jet printed and subsequently plated lines are, in these examples,slightly wider than the laser ablated gold lines due to the wetting ofthe ink just before it is tack cured using the UV lamp attached to theprint head mount. The electroless copper plating step does not appear tosignificantly affect the average line width. The same can also be saidof electroless gold plating. On the other hand, the immersion goldprocess appears to result in a significant increase in the average widthof the lines, potentially signifying that the second metal 60, such asgold, deposited through this method is normally of lower density.

FIGS. 6-9 contain example images of the thin-film catalytic ink, whichhave been plated with electroless copper, electroless gold and immersiongold. In each case, faint borders can be seen on the edges of the lines,which is due to the slightly increased thickness in these areas createdduring the drying process for this ink. The lines are also clearly muchwider than those produced using the standard CIT ink (FIGS. 2-5), as thesolvent base of the formulation promotes increased substrate wetting.

The line width and raggedness of a specific section of the printed andplated circuits were analyzed using the ImageXpert™ image qualityanalysis system. The change in these values, as the printed catalyticink sections were plated with copper and then further with gold, wastracked during this investigation. The specific sections chosen for thisanalysis were the two parallel electrodes at the center of the circuittemplate. See center of FIG. 1A. The edges of the lines show good edgeacuity, though they exhibit greater raggedness when compared to thoselines produced by laser ablation.

Tables 1 and 2, below, depict an example of the ImageXpert™ sequenceused to generate the data shown further below in Tables 3, 5 and 6,pertaining to the CIT ink Examples 1-3.

TABLE 1 Device Report: Line Intercolour Bleed SQ 28/8/56 1:22 StatMeasurement Name Value Nominal Minimum Maximum <F> Left: Top edge 2.99930.000 10.000 30.000 Raggedness <F> Left: Bottom 2.558 30.000 10.00030.000 Edge Raggedness <F> Left: Width 460.353 50.00 25.000 75.000 <F>Right: Top 2.443 0.000 0.000 0.000 Edge Raggedness <F> Right: Bottom3.132 0.000 0.000 0.000 Edge Raggedness <F> Right: Width 449.590 50.00025.000 75.000 <F> Ratio 1.024 0.000 0.000 0.000

TABLE 2 Statistics Report: Line Intercolour Bleed SQ 68 DevicesInspected, 50 Pass (73.5294%) Measurement Name Mean Std. Dev. MinimumMaximum Left: Top edge 8.5233 7.8691 0.0000 35.5747 Raggedness Left:Bottom Edge 16.7440 30.7109 0.0008 151.7476 Raggedness Left: Width583.7745 1009.2000 0.0219 4999.2430 Right: Top Edge 10.2303 8.83180.0002 39.3994 Raggedness Right: Bottom Edge 13.8239 24.0036 0.0002114.0403 Raggedness Right: Width 508.9540 881.6408 0.0189 4199.7020Ratio 1.0458 0.1050 0.9014 1.4521Line Width:

Tables 3 and 4 contain the line width measurements of the samplesprinted with CIT ink (or thin-film CIT ink) and then plated withelectroless copper and further with electroless or immersion gold. Thewidth of the corresponding lines in a gold circuit from a prior artlaser ablation production method is noted for comparison. Table 3 is forthe CIT ink samples (Examples 1-3), whereas Table 4 is for the thin-filmCIT ink samples (Examples 4-6).

TABLE 3 ImageXpert ™ line width measurements of CIT ink-based samplesLine Width/μm Line (1) Line (2) Standard Standard Sample AverageDeviation Average Deviation Gold circuit 507 0.2 507 0.2 template CITInk 514 40.6 530 58.8 CIT ink plated 509 41.7 496 56.5 with electrolesscopper CIT ink plated 512 35.7 483 73.2 with copper and electroless goldCIT ink plated 573 58.6 571 35.9 with copper and immersion gold

TABLE 4 ImageXpert ™ line width measurements of thin-film CIT ink-basedsamples Line Width/μm Line (1) Line (2) Standard Standard Sample AverageDeviation Average Deviation Gold circuit 507 0.2 507 0.2 templateThin-film ink 757 79.7 746 84.0 plated with electroless copper Thin-filmink 666 81.7 697 70.3 plated with copper and electroless gold Thin-filmink 760 58.1 659 126.2 plated with copper and immersion goldEdge Acuity:

The raggedness measurements of the two center electrodes in each sampleare collected in Tables 5-8. Tables 5 and 6 are for the CIT ink samples(Examples 1-3), whereas Tables 7 and 8 are for the thin-film CIT inksamples (Examples 4-6). Once again, the measurements for a prior artlaser ablated gold circuit are included for comparison. The edgeraggedness of the printed and plated strips is greater than the laserablated circuits.

TABLE 5 ImageXpert ™ line (1) raggedness measurements of CIT ink-basedsamples Raggedness of Line (1)/μm Top of Line Bottom of Line StandardStandard Sample Average Deviation Average Deviation Gold circuit 0.7840.020 0.761 0.020 template CIT Ink 5.099 1.849 5.293 1.689 CIT inkplated 5.167 3.881 5.571 4.493 with electroless copper CIT ink plated3.641 0.304 4.014 1.302 with copper and electroless gold CIT ink plated6.379 2.147 5.360 1.590 with copper and immersion gold

TABLE 6 ImageXpert ™ line (2) raggedness measurements of CIT ink-basedsamples Raggedness of Line (2)/μm Top of Line Bottom of Line StandardStandard Sample Average Deviation Average Deviation Gold circuit 0.9700.020 0.996 0.020 template CIT Ink 8.1000 6.414 6.118 1.912 CIT inkplated 5.837 3.137 5.177 2.299 with electroless copper CIT ink plated4.319 2.361 4.343 1.063 with copper and electroless gold CIT ink plated6.182 1.277 4.502 1.264 with copper and immersion gold

Regarding the thin-film CIT ink Examples 4-6, the greater wetting ofthis ink compared to standard CIT ink is also reflected in theraggedness values shown in Tables 7 and 8, below.

TABLE 7 ImageXpert ™ line (1) raggedness measurements of thin-film CITink samples Raggedness of Line (1)/μm Top of Line Bottom of LineStandard Standard Sample Average Deviation Average Deviation Goldcircuit 0.784 0.020 0.761 0.020 template Thin-film ink 9.554 8.38010.811 7.210 plated with electroless copper Thin-film ink 14.257 11.2998.175 6.067 plated with copper and electroless gold Thin-film ink 4.3131.963 7.877 6.895 plated with copper and immersion gold

TABLE 8 ImageXpert ™ line (2) raggedness measurements of thin-filmcatalytic ink samples Raggedness of Line (2)/μm Top of Line Bottom ofLine Standard Standard Sample Average Deviation Average Deviation Goldcircuit 0.970 0.020 0.996 0.020 template Thin-film ink 10.016 6.3779.324 7.372 plated with electroless copper Thin-film ink 10.107 4.03612.763 8.569 plated with copper and electroless gold Thin-film ink 6.6094.282 7.903 4.227 plated with copper and immersion gold

D. ELECTRICAL RESISTANCE

The resistance of the copper and gold plated samples was measured acrossthe length of one electrode. Such length is exemplified as running fromreaction end 91 to contact end 92 (see FIG. 1A). The results are shownin Tables 9 and 10, below. The resistance of the prior art laser ablatedgold circuits across this area is much greater than that for the printedand plated samples. Additionally, the presence of the gold plated on thetop of the copper does not appear to affect the resistance of the strip,regardless of the method used for its deposition, i.e., immersion orelectroless plating.

TABLE 9 Conductivity of CIT ink-based copper and gold-plated samplesSample Average Resistance (O) Gold circuit template 89.3 CIT ink platedwith electroless copper 3.2 CIT ink plated with electroless copper 3.2and electroless gold CIT ink plated with electroless copper 3.1 andimmersion gold

Also, for the thin-filmed CIT ink, (FIGS. 6-9), the resistance of thetop electrode was measured for each copper plated sample. This was thenrepeated after plating with gold and the average resistance values areshown in Table 10. It can be seen that the resistance and thereforeconductivity of the printed and copper-plated samples of thin-layer CITink are the same or similar regardless of whether they are plated usingan immersion or electroless gold plating process. This was also observedwith the standard CIT ink copper-plated samples, in Table 9 above.

TABLE 10 Conductivity of thin-film CIT ink-based copper and gold platedsamples Sample Average Resistance (O) Gold circuit template 89.3Thin-film catalytic ink plated with 2.4 electroless copper Thin-filmcatalytic plated with electroless 2.8 copper and electroless goldThin-film catalytic plated with electroless 2.7 copper and immersiongold

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges, equivalents, and modifications that come within the spirit ofthe inventions defined by following claims are desired to be protected.All publications, patents, and patent applications cited in thisspecification are herein incorporated by reference as if each individualpublication, patent, or patent application were specifically andindividually indicated to be incorporated by reference and set forth inits entirety herein.

The invention claimed is:
 1. A biosensor test member, comprising: anelectrically conductive first layer comprising a first metal in anelectrode pattern on a substrate such that said first layer has at leasttwo electrode layer portions that are spaced from each other on saidsubstrate; and an electrically conductive second layer comprising asecond metal and located on and substantially coinciding with saidelectrically conductive first layer such that said electricallyconductive second layer has at least two second layer electrodesportions that are spaced from each other on said substrate, wherein saidsecond metal is different from said first metal, and said first metaland said second metal being at least partially sintered together, andwherein said first metal and said second metal each are in a cured inkcarrier of the respective first layer and second layer.
 2. The testmember of claim 1 wherein said first and second metals are at leastpartially sintered by exposing them to a low temperature photonicenergy.
 3. The test member of claim 2, wherein said low temperaturephotonic energy maintains the temperature of said substrate below asubstrate damage temperature, and wherein said substrate is nottemperature damaged.
 4. The test member of claim 1, and furthercomprising: a first reference metallic electrical trace and a secondreference metallic electrical trace on said substrate; and, wherein saidfirst reference metallic electrical trace is more cured than said secondreference metallic electrical trace, wherein a differential electricalresistivity exists between said traces sufficient to allow machinereading of test strip attributes based on said differential.
 5. The testmember of claim 1, wherein said electrode pattern comprises at least apair of edges spaced from each other on said substrate, said edges eachhaving an average edge acuity ratio of less than about 20/μm and astandard deviation of said ratio of less than about 15/μm.
 6. The testmember of claim 1, and further comprising a third layer of a reagent onsaid electrically conductive second layer, wherein said second metal issubstantially non-reactive to said reagent.
 7. The test member of claim3, and further comprising a third layer of a reagent on saidelectrically conductive second layer, wherein said second metal issubstantially non-reactive to said reagent.
 8. The test member of claim2, wherein said low temperature photonic energy maintains thetemperature of said substrate below a substrate damage temperaturewherein said substrate is not temperature damaged.
 9. The test member ofclaim 8, wherein said first metal and said second metal each are carriedin a cured ink carrier of the respective first layer and second layer.10. The test member of claim 9, wherein said electrode pattern comprisesat least a pair of edges spaced from each other on said substrate, saidedges each having an average edge acuity ratio of less than about 20/μmand a standard deviation of said ratio of less than about 15/μm.
 11. Thetest member of claim 10, and further comprising a third layer of areagent on said electrically conductive second layer, wherein saidsecond metal is substantially non-reactive to said reagent.